Tumors of the central nervous system account for approximately 2% of all cancer deaths, and are the second largest cause of cancer death in the pediatric population. Among men 15-54 years old, brain tumors are the third most frequent cause of cancer death, and among women 15-34 years old, they are 4th most frequent. This project is designed to identify new sites of altered DNA copy number on chromosomes by using a newly developed methology called "comparative genomic hybridization" (CGH). This method allows us to map increases and decreases of DNA copy number onto normal human chromosomes, and has already identified candidate areas previously unrecognized in tumors. Our major emphasis will be to map and validate candidate areas of decreased and increased DNA copy number in gliomas. A major technical emphasis will be fluorescence in situ hybridization (FSH) to identify genetic aberrations both in single primary brain tumor cells and in DNA isolated from brain tumors.